In a recent assembly line of vehicles or the like, an elongated rectangular-shaped plastic footrest plate is attached to a workpiece such as a vehicle body as often as required. Generally, in order to facilitate the attaching operation of the footrest plate, a pair of mounting holes are formed in the workpiece, and a pair of anchor clips are provides on the rear side opposite to the footrest side of the footrest plate in alignment with the pair of mounting holes. Then, the pair of clips are inserted into the corresponding mounting holes to fix the footrest plate to the workpiece. The pair of mounting holes are formed at predetermined positions of the workpiece with leaving a predetermined distance therebetween. Correspondingly, the pair of clips are provided at predetermined positions of the rear side of the footrest plate with leaving a predetermined distance therebetween.
The respective positions and the distance for the pair of mounting holes should match with those for the pair of clips to allow the clips to be inserted into the corresponding mounting holes. However, complicated processes are required to form the mounting holes and the clips with a high degree of positioning accuracy, which leads to undesirably increased cost. From this point of view, each of the mounting holes is formed with a predetermined positional tolerance, and the clips are formed with a predetermined clearance for compensating a misalignment caused by the tolerance. In a conventional footrest plate, one of the clips is formed as a reference clip, and the other clip is formed smaller by a clearance thereof. In this case, if the attached footrest plate is applied with a heavy load from a driver's foot rested thereon, the region of the footrest plate around the reference clip can be secured, whereas the remaining region around the other clip is displaced by the clearance. This allows the footrest plate to be rotated several or more degrees around the reference clip, and such a rotational movement is repeatedly caused as a consequence of changes of the direction of the load, resulting in undesirable wobbling movement of the footrest plate.
FIGS. 1A to 1C show a conventional footrest plate 1. The footrest plate 1 is composed of an elongated rectangular-shaped plastic plate member. The footrest plate has a front surface serving as a footrest side 2 formed with a number of protrusions 3 for preventing a foot of a driver or the like from slipping. The rear side 5 of the footrest plate opposite to the footrest side 2 is provided with a pair of anchor clips 6 and 7 to be fixedly received into a pair of corresponding mounting holes which are formed in a workpiece such as a vehicle body or a seat member fixed to the vehicle body with protruding from the rear side 5 and leaving a certain distance therebetween. Each of the clips 6 and 7 includes a shank having a rectangular cross-sectional insertion portion in conformity with the corresponding mounting hole of the workpiece formed in a rectangular shape. In the pair of mounting holes, their positioning accuracy and the distance therebetween are designed with predetermined tolerances. Further, one of the clips is formed with a clearance to allow its misalignment caused by the tolerances to be compensated by the cross-sectional dimension of the insertion portion of the shank. As shown in FIG. 1C, according to a conventional footrest plate, one clip 7 is formed as a reference clip having the same dimension as that of the corresponding mounting hole 9, and the shank of the other clip 6 is formed to define a pair of longitudinal sides in cross section each having a length shorter than that of each longitudinal side of the corresponding mounting hole 10 by a clearance 11.
The above conventional footrest plate fastening has an advantage of providing a simple attaching operation in which the footrest plate is attached only by inserting the clips into the mounting holes without any tool. However, the conventional footrest plate fastening can cause undesirable wobbling movement of the footrest plate by a heavy load applied from a foot of a drivers or the like to the footrest plate. This wobbling movement will be described with reference to FIGS. 2A and 2B in which the clips and the mounting holes are enlarged in an exaggerated form, and the respective distances between the clips and between the mounting holes are shorten for the sake of simplicity of descriptions. As shown in FIG. 1A, in the condition after the footrest plate is attached to the workpiece, the clips 6 and 7 are generally located at the illustrated positions in alignment with the corresponding mounting holes 9 and 10. In this condition, when a driver or other passenger braces his/her foot with placing the foot 11 on the footrest plate, a heavy load is applied to the footrest plate 1 in the direction shown by the arrow 13. Then, this load moves the footrest plate by the clearance between each of the clips and the corresponding mounting hole, as shown FIG. 2B. In FIG. 2B, the reference clip 7 is slightly moved to one of the sides of the mounting hole 9 against one of the elastic engagement pawl of the reference clip and fixed thereat, whereas the other clip 6 is rotationally moved with respect to the mounting hole 10 in the direction shown by the arrow 15 around the point 14 in the reference clip 7 according to the clearance 11. When the load from the bracing force of the foot is turned down and the load 13 is reduced, the clip 6 is moved to the center of the mounting hole 10 by the action of the elastic engagement pawls of the clip 6 so as to return the footrest plate to the original position. When the foot is braced again, the footrest plate is re-moved in the direction shown by the arrow 15. As a result, the footrest plate is rotated in the range of the distance 17. Even though this rotational angle is small, the foot of a driver or other passenger is repeatedly wobbled by the rotational movements as a consequence of changes of the load. This is objectionable from a fundamental performance of the footrest plate.
Japanese Utility Model Laid-Open No. 62-39007 discloses a assembly for attaching a molding such as side guard molding to a vehicle body. In this assembly, a plurality of clip are fixed to the molding, and a corresponding number of grommets are fixed to a vehicle body. Then, the clips are inserted into the corresponding grommets to attach the molding to the vehicle body. For allowing the clips to be adequately received into the corresponding grommets even if the distance between the adjacent clips or grommets is varied by dimensional tolerances or thermal expansions, one of the adjacent grommets is arranged to have a longitudinal length greater than that of the other grommet. The assembly described in this publication does not include any suggestion on attachment of a footrest plate. Further, a misalignment caused by tolerances or thermal expansions is compensated by only one grommet. Thus, even if this assembly can be applied to a footrest plate, the aforementioned problem of the rotational or wobbling movement cannot be solved.
Japanese Utility Model Laid-Open No. 01-162847 discloses a assembly for attaching a garnish to a vehicle body. In this assembly, a plurality of clips are fixed to the rear side of the garnish through respective retainers with leaving a predetermined distance therebetween, and a plurality of mounting holes are formed in the vehicle body at corresponding positions with leaving a predetermined distance therebetween. One of the retainers is formed with an L-shaped notch, and each of the remaining retainers is formed with a straight notch extending in one direction. Each of these notches has an opening through which the clip is detachably received. The clip received in the L-shaped notch is held by the corresponding mounting hole so as not to move in the longitudinal direction of the straight notch. As with the aforementioned assembly, the assembly described in this publication does not include any suggestion on attachment of a footrest plate. In particular, this assembly is intended to detachably hold the garnish, and is unsuited for a measure for reducing the rotational or wobbling movement of a footrest plate.
It is therefore an object of the present invention to provide a footrest plate and a footrest plate mounting assembly capable of reducing rotational or wobbling movement of the footrest plate attached to a vehicle body or the like while maintaining a simple attaching operation for the footrest plate.